UNIVERSITY   OF   CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL   EXPERIMENT   STATION 

CIRCULAR  No.  233 
March,  1922 

ARTIFICIAL  INCUBATION 

By  J.  E.  DOUGHERTY 


Selecting  Eggs  for  Hatching. — Care  and  judgment  should  be  exer- 
cised in  the  selection  of  the  eggs  that  are  to  produce  the  future  layers. 
These  eggs  should  be  rigidly  selected  for  (1)  fairly  large  size,  (2)  uni- 
formity of  size,  (3)  regular  shape,  (4)  uniformity  of  shape,  (5)  color, 
(6)  uniformity  of  color,  and  (7)  strong  shell  texture.  Eggs  for  in- 
cubation should  weigh  from  24  to  26  ounces  per  dozen,  as  those  of 
fairly  large  size  will  hatch  heavier  chicks  than  small  eggs.  The  small 
chick  is  seriously  handicapped  when  forced  to  compete  for  food  and 
warmth  with  larger,  stronger  chicks.  Hatching  eggs  should  also  be 
uniform  in  size  for  those  too  large  or  too  small  make  turning  difficult, 
and  they  should  have  strong  shells  for  eggs  with  weak  shell  texture 
break  very  easily  in  turning. 

There  is  evidence  that  size,  shape  and  color  of  the  egg  are  inherited 
characters,  for  example,  eggs  of  large  size  are  a  breed  characteristic 
of  the  Minorca,  white  eggs  a  breed  characteristic  of  the  Leghorn,  and 
brown  eggs  a  breed  characteristic  of  the  Plymouth  Rocks.  Therefore, 
continued  careful  selection  of  hatching  eggs  should  result  in  a  few 
years  in  the  development  of  a  flock  producing  uniformly  large,  well- 
shaped,  evenly  colored  eggs  of  good  shell  texture,  because  like  tends 
to  produce  like.  The  exercise  of  care  and  judgment  in  the  selection 
of  hatching  eggs  will  not  only  facilitate  handling  during  incubation, 
but  will  also  make  for  the  building  up  of  a  flock  that  should  average 
a  larger  percentage  of  ' '  extras, ' '  and  every  increase  in  the  number  of 
good-sized  eggs  laid  by  a  flock  means  an  increased  profit  to  the  owner. 

Saving  Eggs  for  Hatching. — Eggs  intended  for  hatching  should  be 
kept  in  a  closed  receptacle  at  a  temperature  of  about  60  degrees  F. 
and  turned  daily.  If  kept  in  open  trays  exposed  to  the  air,  more  or 
less  moisture  will  evaporate  from  the  eggs  and  injure  their  hatching 
quality.  A  30-dozen-size  egg  case  provided  with  a  hinged  cover  is  an 
excellent  container  in  which  to  save  hatching  eggs.  The  selected  eggs 
are  put  in  the  egg  case  each  day,  the  empty  fillers  replaced  and  the 


2  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

case  closed.  To  turn  the  eggs,  lay  the  case  on  one  side  the  first  day, 
on  one  end  the  second  day,  on  the  other  side  the  third  day,  etc. 
Revolving  the  case  in  this  way  every  day  turns  the  eggs  one  quarter 
and  keeps  them  on  their  sides,  which  is  the  preferable  position  for 
eggs  before  and  during  incubation.  Hatching  eggs  should  not  be  more 
than  10  days  to  two  weeks  old  when  set.  The  sooner  they  are  set  the 
better. 

Getting  the  Incubator  Ready. — Before  the  beginning  of  the  hatch- 
ing season  each  year,  the  incubator  equipment  should  be  carefully 
gone  over.  Each  incubator  should  be  overhauled  to  see  that  all 
mechanical  parts  are  in  good  order  and  working  freely.  One  or  two 
extra  thermometers  and  a  few  wicks  should  always  be  kept  on  hand. 

Locating  the  Incubator. — Place  the  machine  in  a  room  where  the 
temperature  remains  fairly  uniform  at  all  times  and  where  there  is 
plenty  of  ventilation  without  drafts.  A  cellar  is  usually  best  because 
it  is  well  protected  from  the  direct  rays  of  the  sun  and  the  tempera- 
ture is  uniformly  low.  A  good  temperature  for  an  incubator  room  is 
60  degrees  F. 

Good  ventilation  can  be  obtained  in  the  incubator  room  by  using 
an  ample  number  of  ventilators  opening  near  the  ceiling  for  the 
ingress  of  fresh  air,  and  by  having  a  6"  to  8"  ventilator  for  the 
removal  of  foul  air.  The  fresh-air  ventilators  should  be  provided 
with  baffles  in  order  to  reduce  the  velocity  of  the  incoming  air  and 
to  direct  it  toward  the  ceiling.  It  will  then  mingle  quietly  with  the 
air  of  the  room  and  not  produce  any  strong  air  currents. 

A  simple  method  of  obtaining  effective  ventilation  as  well  as  good 
lighting  of  an  incubator  room  is  that  of  placing  transom  or  cellar  sash 
about  two-thirds  of  the  way  up  the  side  walls  toward  the  ceiling.  They 
should  be  spaced  approximately  six  feet  apart  on  centers  and  hinged 
at  the  bottom  so  as  to  swing  in.  A  triangular  wooden  shield  should  be 
placed  on  each  side  of  the  window  (see  Fig.  1)  to  force  the  incoming 
fresh  air  over  the  top  of  the  window  when  open.  These  shields  will 
also  support  the  window  when  it  is  open.  A  light  frame  covered  with 
coarse,  light-weight  burlap  and  hinged  to  the  wall  just  above  the 
window  so  as  to  rest  on  the  wooden  shields  and  fully  cover  the  opening 
over  the  shields,  will  check  the  velocity  of  the  incoming  fresh  air  on 
windy  days  sufficiently  to  prevent  strong  air  currents  in  the  incubator 
room.  Such  air  currents  might  cause  the  incubator  lamps  to  flicker 
and  blow  out  or  affect  the  temperatures  of  some  machines. 

One  exhaust  ventilator,  6"  to  8"  square  inside,  should  be  provided 
for  approximately  every  300  square  feet  of  floor  space.     This  venti- 


Circular  233] 


ARTIFICIAL    INCUBATION 


lator  should  be  built  with  the  bottom  18"  above  the  floor  and  the  top 
extending  well  above  the  highest  point  of  the  roof.  The  higher  the 
top  of  this  ventilator,  the  stronger  will  be  the  suction.  An  especially 
designed  metal  ventilator  cap  placed  on  the  top  of  the  ventilator  will 
also  increase  its  suction. 

Having  located  the  incubator,  level  it  with  a  spirit  level.  Leveling 
is  very  important,  for  if  the  machine  is  not  level,  one  part  of  the  egg 
tray  will  be  higher  than  another,  and  the  eggs  in  that  part  will  there- 
fore obtain  more  heat  than  the  others. 


Fig.  1. — Interior  of  a  brooder  house  showing  how  wooden  shields  are  used  at 
sides  of  windows  to  divert  all  incoming  fresh  air  over  tops  of  windows  when  open. 
Windows  open  inward  at  top. 

Disinfection. — Before  and  after  every  hatch,  the  incubator  should 
be  thoroughly  washed  and  sprayed  and  the  movable  parts  placed  in 
the  sun  to  dry.  Thoroughly  cleanse  every  part  with  soap,  water  and 
a  good  scrubbing  brush.  A  few  hours  before  putting  in  the  eggs 
spray  all  parts  of  the  interior  of  the  incubator  with  a  spray  pump, 
using  about  a  two  per  cent  solution  of  some  good  disinfectant,  such 
as  a  cresol  compound  or  any  of  the  "eum"  preparations.  The  fumes 
of  the  disinfectant  will  penetrate  every  crack  in  the  hot  interior  of 
the  egg  chamber  and  the  vapors  remaining  when  the  eggs  are  put  in 
will,  to  some  extent,  disinfect  the  exterior  of  the  eggs.     To  disinfect 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

thoroughly  the  surfaces  of  the  eggs,  dip  them  fairly  rapidly  in  95  per 
cent  pure,  non-beverage  alcohol  just  before  putting  them  into  the 
incubator. 

The  Lamp. — Every  season  the  lamp  should  be  thoroughly  cleaned, 
the  burner  boiled  in  a  solution  of  washing  soda  and  a  new  wick  put 
in,  if  necessary,  before  the  machine  is  started. 

In  beginning  the  hatch,  use  a  medium  flame,  and  adjust  the  thermo- 
stat to  it.    If  too  small  a  flame  is  used  to  start  with,  the  flame  cannot 


Y?nr)nnnry^nnnn^^  \  I 


J 


-^r. 


\\aam 


\    N. 


a  v 


Fig.  2. — Cross-section  of  a  hot-air  heated  incubator  showing  the  method  of 
regulating  the  temperature,  the  ventilation  system,  and  the  general  construction. 

(a)  Counterpoise  weight ;  (b)  regulator  arm;  (o)  connecting  rod;  (d)  thumb 
nut;  (e)  pivot  casting;  (/)  heater  disc;  (g)  cotton  batting  filling  between  inside 
and  outside  cases;  (h)  thermostat;  (i)  egg  chamber;  (j)  moisture  pan  filled  with 
sand  kept  wet;  (fc)  nursery;  (m)  bottom  ventilator  for  escape  of  air  from  egg 
chamber;  (ft)  insulation  in  bottom  of  incubator;  (p)  one  of  four  pipes  to  dis- 
charge air  from  above  level  of  eggs  into  false  bottom  beneath  egg  chamber;  (r) 
fresh  air  intake;  O)  outlet  for  escape  of  lamp  fumes.  No  fumes  can  get  into 
machine. 


be  turned  low  enough  at  the  end  of  the  hatch,  in  warm  weather,  to 
keep  the  temperature  from  running  up.  If  too  high  a  flame  is  used 
the  lamp  will  smoke. 

The  lamp  should  be  cleaned  and  filled  every  morning  after  turn- 
ing the  eggs.  If  filled  before  turning  the  eggs,  the  hands,  being 
smeared  with  oil  from  the  lamp,  will  leave  a  coating  of  oil  on  the 
eggs  and  cause  serious  injury  to  the  growing  embryos.  Trim  the  wick 
with  a  cloth  by  simply  rubbing  off  the  charred  crust  and  then  wipe 
away  all  dirt  and  oil  from  all  parts  of  the  lamp  before  replacing  in 


Circular  233]  artificial  incubation  5 

the  incubator.  In  trimming,  cover  the  end  of  the  finger  with  a  cloth 
and  turn  the  wick  just  high  enough  to  expose  the  charred  part  above 
the  top  edge  of  wick  tube.  Rub  off  the  charred  crust  by  rubbing  in 
one  direction  only;  this  causes  all  the  threads  of  the  wick  to  lie 
smoothly  in  one  direction  and  results  in  a  more  even  flame.  Then 
turn  the  wick  up  about  one-sixteenth  of  an  inch  and  pat  down  the 
corners  lightly  to  prevent  high  corners  on  the  flame  which  would  cause 
smoking.  A  flame  that  is  straight  across  the  top  and  rounded  at  the 
corners  gives  the  most  heat  and  will  not  smoke. 

Thermometer. — In  order  to  be  certain  that  the  thermometer  is  cor- 
rect, the  operator  should  test  it  with  a  clinical  thermometer.  Place 
both  thermometers  in  hike-warm  water  with  bulbs  close  together  and 
while  stirring,  add  hot  water  slowly  until  the  clinical  thermometer 
registers  103  degrees.  Observe  whether  the  incubator  thermometer 
gives  a  similar  reading.  If  not,  the  operator  knows  that  at  103  de- 
grees the  incubator  thermometer  reads,  perhaps,  102^2  degrees,  and 
he  must  allow  for  this  error  in  operating  his  incubator.  Faulty  ther- 
mometers have  caused  more  damage  in  the  way  of  poor  hatches  than  is 
generally  realized. 

Temperature. — In  all  incubators  the  temperature  is  regulated  or 
controlled  by  a  thermostat.  The  all-metal  thermostat  (see  Fig.  2) 
consists  of  three  pieces  of  metal  riveted  together  at  the  ends  and 
is  designed  on  the  principle  that  different  metals  expand  different 
definite  amounts  for  every  degree  F.  rise  in  temperature  and  contract 
the  same  amounts  for  every  degree  F.  fall  in  temperature.  The  cen- 
tral piece  of  metal  {~h,  Fig.  2),  does  not  expand  or  contract  as  much 
for  every  degree  of  change  in  temperature  as  do  the  two  outside  pieces. 
As  a  result,  since  all  three  pieces  are  riveted  at  the  ends,  the  two 
outside  pieces,  expanding  more  rapidly  than  the  central  piece,  are 
forced  outward  in  the  middle  when  the  temperature  rises.  This  buck- 
ling or  spreading  apart  of  the  two  outside  pieces  of  metal  in  the 
thermostat  causes  a  downward  pull  on  the  connecting  rod  (c),  which 
in  turn  pulls  on  the  lever  arm  (b)  and  raises  the  disc  (/)  off  of  the 
heater. 

When  the  temperature  in  the  incubator  rises  above  the  desired 
temperature,  the  expansion  of  the  thermostat  lifts  the  disc  from  one- 
half  inch  to  one  and  one-half  inches  above  the  heater,  allowing  the 
surplus  heat  to  escape.  As  soon  as  the  temperature  returns  to  its 
proper  place,  the  disc  is  again  lowered.  If  the  temperature  of  the 
machine  should  drow  below  the  "running"  temperature,  the  thermo- 
stat will  contract  and  allow  the  disc  to  settle  down  on  the  heater,  thus 


0  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

tightly  closing  the  opening  and  forcing  all  the  heat  into  the  egg  cham- 
ber. When  the  temperature  is  properly  regulated,  the  disc  should 
stand  about  one-sixteenth  to  one-eighth  inch  above  the  opening  in  the 
top  of  the  heater.  There  are  a  number  of  different  kinds  of  thermo- 
stats or  heat-regulating  devices  used  on  different  makes  of  machines, 
but  all  are  based  on  the  principle  of  expansion  and  contraction  of  a 
thermostatic  device  within  the  egg  chamber  to  control  the  amount  of 
heat  entering,  and  thus  automatically  regulate  the  temperature  of  the 
egg  chamber. 

In  the  type  of  heater  shown  in  Fig.  2,  the  fumes  from  the  lamp 
cannot  get  into  the  egg  chamber,  but  must  escape  through  the  open- 
ing (s).  The  fresh  air  (as  shown  by  arrows)  is  heated  by  the  lamp 
as  it  is  drawn  into  the  opening  (r).  It  passes  into  the  top  of  the 
incubator  and  then  diffuses  through  a  burlap  or  muslin  diaphragm 
into  the  egg  chamber.  After  circulating  around  the  eggs,  absorbing 
the  carbon  dioxide  thrown  off  by  the  eggs  and  giving  up  oxygen,  the 
air  current  passes  through  the  openings  at  the  sides  of  the  egg  cham- 
ber and  escapes  through  the  bottom  of  the  machine. 

The  temperature  throughout  the  hatch  should  be  102  degrees  when 
the  center  of  the  thermometer  bulb  is  on  a  level  with  the  tops  of  the 
eggs.  If  the  thermometer  is  hung  so  that  the  center  of  the  bulb  is 
above  the  tops  of  the  eggs,  the  temperature  must  be  run  higher  accord- 
ing to  the  height  of  the  bulb  above  the  eggs.  The  heat  in  nearly  all 
incubators  comes  into  the  egg  chamber  from  the  top  and  the  nearer 
the  thermometer  is  to  the  top  of  the  egg  chamber  the  higher  it  will 
read.  While  chicks  are  hatching  the  temperature  can,  and  often  does, 
run  up  to  104  degrees  without  doing  any  harm. 

Ventilation. — Good  ventilation  of  the  egg  chamber  is  a  very  im- 
portant part  of  the  process  of  incubation.  During  the  growth  of  the 
embryo,  it  has  for  its  food  supply  the  stored-up  food  within  the  egg. 
In  order  to  utilize  this  stored-up  food  and  transform  it  into  new  body 
tissues,  heat,  and  muscular  action  (such  as  the  pumping  of  the  blood 
through  the  blood  vessels  that  radiate  through  all  parts  of  the  develop- 
ing egg),  oxygen  is  absolutely  necessary.  Without  oxygen,  growth 
could  not  go  on  and  the  embryo  would  die.  The  net-work  of  blood 
vessels  which  extend  in  great  numbers  close  to  the  inside  of  the  shell 
and  to  the  air-cell,  takes  up  oxygen  from  the  incoming  fresh  air  and 
throws  off  carbon  dioxide,  which  is  given  off  as  a  waste  product  by 
the  growing  body  tissues.  Therefore,  plenty  of  fresh  air  is  essential 
to  the  production  of  strong,  vigorous  chicks.  Briefly  stated,  the  devel- 
oping embryo  breathes  in  fresh  air  through  the  pores  of  the  shell  and 


Circular  233]  ARTIFICIAL  INCUBATION  7 

from  the  air-cell.  It  exhales  poisonous  carbon  dioxide  through  the 
pores  of  the  shell  and  into  the  air-cell.  The  ventilation  of  the  incu- 
bator should  be  such  as  to  carry  fresh  air  into  the  egg  chamber  as 
rapidly  as  it  is  needed  and  to  carry  away  the  carbin  dioxide  as  rapidly 
as  it  is  given  off.  Insufficient  ventilation  will  rob  the  chicks  of  vitality 
even  though  it  may  not  prevent  hatching.  Too  much  ventilation  can- 
not be  given,  provided  proper  temperature  and  moisture  conditions 
are  maintained  in  the  egg  chamber.  It  is  better  to  give  too  much 
rather  than  risk  too  little. 

Insufficient  ventilation  in  the  egg  chamber,  which  is  not  always 
readily  detected  during  the  first  19  days  of  the  hatch,  will  reveal  itself 
after  a  good  many  of  the  chicks  have  hatched  out.  The  panting  of 
the  chicks  after  hatching  is  invariably  caused  by  too  little  ventilation, 
rather  than  by  too  much  heat.  Even  though  the  hatch  is  not  over, 
more  ventilation  must  be  given  if  the  chicks  already  hatched  are  not 
to  be  weakened. 

Moisture. — The  process  of  exhaling  in  the  developing  egg  is  closely 
analogous  to  that  in  human  beings.  The  exhaled  air  is  laden  with 
moisture,  and  it  is  as  a  result  of  giving  off  used  moisture  in  this  way 
that  the  eggs  "dry  down"  during  embryonic  growth.  This  drying 
down  causes  a  gradual  loss  of  the  water  content  of  the  egg  and  a  cor- 
respondingly gradual  increase  in  the  size  of  the  air-cell.  When  the 
air  passing  through  the  egg  chamber  is  very  dry,  it  not  only  takes  up 
and  carries  off  the  moisture  naturally  exhaled  by  the  egg,  but  also 
passes  through  the  porous  shell  and  absorbs  still  more  moisture.  By 
such  excessive  drying  down  of  the  egg  the  embryo  will  be  injured. 
Nature  supplies  the  egg  with  just  enough  water  to  enable  it  to  carry 
on  its  life  processes  and  to  evaporate  gradually  by  the  process  of 
exhalation.  From  this  we  can  clearly  understand  the  vital  necessity 
of  having  the  air  passing  through  the  egg  chamber  sufficiently  satu- 
rated with  moisture  to  prevent  undue  evaporation  of  the  moisture 
from  the  egg.  Sixty  per  cent  humidity  is  generally  considered 
adequate. 

It  is  evident  that  ventilation  and  moisture  conditions  are  closely 
related  and  cannot  be  considered  separate  problems.  Geographical 
location,  time  of  year,  and  other  factors  must  determine  whether  arti- 
ficial means  of  adding  moisture  to  the  air  entering  the  egg  chamber 
is  necessary  or  not.  In  the  better  types  of  incubators,  ventilation  is 
very  well  taken  care  of,  so  that  the  chief  problem  to  consider  is  the 
maintenance  of  sufficient  moisture  in  the  circulating  air.  One  should 
always  follow  the  instructions  sent  out  by  the  incubator  manufacturer 


8  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

in  this  regard  until  sufficient  experience  has  been  gained  to  enable  one 
to  act  intelligently  in  making  any  change  that  may  appear  advisable. 
The  increase  in  size  of  the  air-cell,  the  drying  of  the  membrane  exposed 
when  the  chick  pips  the  shell,  the  collection  of  moisture  on  the  inside 
of  the  glass  of  the  incubator  door  (see  following  page),  and  the  ease 
with  which  the  chicks  break  from  the  shell,  will  serve  as  definite 
guides  in  properly  regulating  moisture  conditions  and  ventilation  in 
artificial  hatching. 

During  the  hatching  period,  frequent  observations  of  the  air-cells 
will  indicate  the  rate  of  evaporation  of  the  egg  and  will  enable  one 

^*^~       ^^""^L Fresh  egg. 

y^— _X^ 7th  day. 

/- _X 14th  day. 

/ \ 19th  day. 


Fig.    3. — Showing  gradual  increase  in   size   of  air-cell  due  to   evaporation   of 
water  during  the  period  of  incubation. 

to  determine  if  too  much  or  too  little  moisture  is  being  supplied. 
Experience  will  soon  teach  one  the  proper  rate  of  evaporation  as  shown 
by  a  gradual  increase  in  the  size  of  the  air-cell.  It  is  a  good  plan  for 
the  beginner  to  set  a  hen  on  the  ground  in  an  out-door  setting  coop 
at  the  same  time  that  he  sets  the  incubator  and  compare  the  increase 
in  the  size  of  the  air-cell  in  both  cases  every  few  days. 

After  the  chicks  have  begun  to  hatch,  a  light  film  of  moisture  or 
a  few  beads  of  water  should  appear  along  the  lower  inside  edge  of 
the  glass  of  the  incubator  door.  Only  a  little  moisture  should  collect 
on  the  inside  of  the  glass  door.  Too  much  humidity  in  the  egg  cham- 
ber is  indicated  at  this  time  by  a  considerable  collection  of  moisture 
on  the  glass  and  can  be  corrected  by  increasing  the  ventilation  or  by 
reducing  the  amount  of  moisture  supplied.  Too  little  humidity  is 
indicated  by  no  moisture  on  the  inside  of  the  glass  door,  and  by  the 
rapid  drying  and  whitening  of  the  shell  membrane  exposed  around 


Circular  233]  ARTIFICIAL  INCUBATION  9 

the  edges  of  the  opening  where  the  chick  has  pipped  the  shell  and 
before  it  has  gotten  out.  As  the  shell  membrane  dries  it  becomes  so 
tough  that  the  check  is  unable  to  tear  through  it  and  dies  in  the  effort 
to  get  out.  The  membrane  should  remain  moist  while  the  chick  is 
breaking  out  of  the  shell,  for  it  is  then  soft  and  easily  torn. 

One  of  the  best  ways  to  supply  needed  moisture  when  using  a 
"non-moisture"  machine,  is  to  keep  the  floor  well  soaked.  The  evapo- 
ration of  moisture  is  in  proportion  to  the  water  surface  exposed  to  the 
air,  so  that  wetting  down  the  floor  exposes  a  large  water  surface  and 
enables  the  air  to  become  well  saturated  before  entering  the  incubator. 
The  purpose  of  such  moisture  is  not  to  supply  it  to  the  eggs,  but  to 
keep  the  air  entering  the  incubator  moist  enough  not  to  take  up  too 
much  moisture  from  the  eggs  and  thus  rob  the  embryos  of  the  water 
they  absolutely  need  in  order  to  develop  into  strong,  lusty  chicks. 

Turning. — Turning  is  usually  begun  from  24  to  48  hours  after  the 
eggs  are  put  into  the  incubator  and  continued  morning  and  night  until 
the  first  egg  pips.  The  turning  periods  should  be  as  nearly  12  hours 
apart  as  possible.  Perhaps  the  easiest  and  best  way  to  turn  is  to  use 
a  rotary  motion,  rolling  the  eggs  slowly  with  the  palms  of  the  hands. 
They  will  not  break  even  if  considerable  pressure  is  used,  provided 
they  are  not  jarred  or  handled  with  sudden  motions.  The  eggs  do 
not  have  to  be  turned  completely  over.  All  that  is  necessary  is  that 
the  eggs  be  shifted  around  a  little  so  that  the  embryos  will  not  stick 
to  the  shells. 

Cooling. — The  purpose  of  cooling  is  to  thoroughly  air  the  eggs  and 
strengthen  the  embryos.  It  corresponds  to  the  opening  of  the  win- 
dows by  the  housewife  each  morning  to  air  the  bedroom.  The  incu- 
bator door  should  not  be  left  open  while  eggs  are  being  cooled.  The 
aim  is  to  cool  the  eggs,  not  the  incubator.  The  hen's  body  temperature 
is  the  same  when  she  returns  to  the  eggs  as  it  was  when  she  left  them. 
So  it  should  be  with  the  incubator. 

In  setting  the  eggs  out  to  cool  do  not  allow  any  part  of  the  tray 
to  project  beyond  the  table  or  incubator,  as  the  eggs  will  then  cool 
unevenly  and  those  in  the  projecting  part  of  the  tray  will  become 
chilled  by  the  time  the  others  are  ready  to  go  back  into  the  machine. 
Begin  cooling  on  the  seventh  day  and  cool  every  evening  when  the 
eggs  are  turned.  Cool  a  little  at  first  and  gradually  lengthen  the  cool- 
ing period  as  the  hatch  advances.  A  most  satisfactory  way  to  tell 
when  the  eggs  are  cooled  sufficiently  is  to  hold  the  small  ends  of 
a  few  to  the  eye.  When  they  feel  barely  warm  the  eggs  are  cooled 
enough.    A  little  experience  will  make  one  expert  in  gauging  the  cool- 


10  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

ing  period.  They  will  cool  down  rapidly  at  first,  but  as  the  embryos 
develop  and  contain  animal  heat  of  their  own  the  cooling  will  take 
place  more  slowly.  In  the  month  of  May,  from  20  to  60  minutes  is 
often  required  to  cool  eggs  that  have  been  in  the  incubator  from  14 
to  18  days.  The  amateur  usually  errs  on  the  side  of  too  little,  rather 
than  on  that  of  too  much  cooling. 

Testing. — Test  on  the  seventh  and  fourteenth  days,  at  night  when 
the  cooling  is  done.  The  first  test  will  remove  all  infertile  eggs  and 
dead  germ  eggs  up  to  that  period.  The  infertile  eggs  are  still  per- 
fectly good  and  can  be  used  for  cooking.  The  writer  has  known  them 
to  be  so  used  and  considers  them  as  good  as  cold-storage  eggs  for 
cooking  purposes.  The  dead  germs  at  the  seventh-day  test  contain 
either  blood  clots  or  blood  rings.    Every  egg  in  which  a  dark  movable 


Dead  germ,  seventh  day.  Fertile  egg,  seventh  day.  Infertile  egg. 

Fig.  4. 

black  spot,  a  little  larger  than  a  pinhead,  with  numerous  radiating 
blood  vessels  is  not  distinctly  visible  at  this  time  should  be  discarded 
as  worthless.  Only  good,  strong  eggs  will  hatch  vigorous  chicks.  On 
the  fourteenth  day  the  strong  eggs  will  be  opaque  and  nearly  black, 
and  if  such  an  egg  can  be  held  still  before  the  tester,  the  embryo  can 
be  seen  to  move.  Dead  germs  at  this  time  contain  either  blood  rings 
or  blood  streaks,  or  are  perfectly  translucent  and  cloudy. 

The  Hatch. — After  the  last  turning,  close  the  incubator  and  do  not 
disturb  it  again  until  the  hatch  is  over,  except  to  fill  the  lamp.  As 
soon  as  all  the  chicks  have  dried  off,  open  wide  the  ventilators,  remove 
the  egg  tray  and  all  eggshells,  and  wedge  open  the  door  with  a  match 
stick  so  as  to  harden  the  little  fellows,  but  do  not  let  the  tempera- 
ture in  the  nursery  go  below  100  degrees  F.  Darken  the  egg  chamber 
by  hanging  a  cloth  in  front  of  the  glass  door  to  keep  the  chicks  from 
picking  at  the  droppings  and  at  each  other's  toes.  After  24  hours 
remove  them  to  the  brooder  in  a  flannel-lined  and  hooded  basket.  A 
chilling  draught  striking  them  at  this  time  would  prove  disastrous. 


STATION  PUBLICATIONS  AVAILABLE  FOR  FREE  DISTRIBUTION 


BULLETINS 


No. 
185 

241. 
246. 
251. 


253. 

261. 
262. 

263. 
266. 

267. 
268. 
270. 


271. 
273. 

275. 

276. 
278. 
279. 
280. 

282. 

283. 
285. 
286. 
287. 
294. 


Report  of  Progress  in  Cereal  Investiga- 
tions. 

Vine  Pruning  in  California,  Part  I. 

Vine  Pruning  in  California,  Part  II. 

Utilization  of  the  Nitrogen  and  Organic 
Matter  in  Septic  and  Imhoff  Tank 
Sludges. 

Irrigation  and  Soil  Conditions  in  the 
Sierra  Nevada  Foothills,  California. 

Melaxuma  of  the  Walnut,  "Juglans  regia." 

Citrus  Diseases  of  Florida  and  Cuba 
Compared  with  Those  of  California. 

Size  Grades  for  Ripe  Olives. 

A  Spotting  of  Citrus  Fruits  Due  to  the 
Action  of  Oil  Liberated  from  the  Rind. 

Experiments  with  Stocks  for  Citrus. 

Growing  and  Grafting  Olive  Seedlings. 

A  Comparison  of  Annual  Cropping,  Bi- 
ennial Cropping,  and  Green  Manures 
on  the  Yield  of  Wheat. 

Feeding  Dairy  Calves  in  California. 

Preliminary  Report  on  Kearney  Vineyard 
Experimental  Drain. 

The  Cultivation  of  Belladonna  in  Cali- 
fornia. 

The  Pomegranate. 

Grain  Sorghums. 

Irrigation  of  Rice  in  California. 

Irrigation  of  Alfalfa  in  the  Sacramento 
Valley. 

Trials  with  California  Silage  Crops  for 
Dairy  Cows. 

The  Olive  Insects  of  California. 

The  Milk  Goat  in  California. 

Commercial  Fertilizers. 

Vinegar  from  Waste  Fruits. 

Bean  Culture  in  California. 


No. 
297 
298 
299 
300 
304 


The  Almond  in  California. 

Seedless  Raisin  Grapes. 

The  Use  of  Lumber  on  California  Farms. 

Commercial  Fertilizers. 

A  Study  on  the  Effects  of  Freezes  on 
Citrus  in  California. 

I.  Fumigation  with  Liquid  Hydrocyanic 
Acid.  II.  Physical  and  Chemical  Pro- 
perties of  Liquid  Hydrocvanic  Aoid. 

I.  The  Carob  in  Cal  fornia.  II.  Nutritive 
Value  of  the  Carob  Bean. 

Plum  Pollination. 

Mariout  Barley. 

Pruning  Young  Deciduous  Fruit  Trees. 

The  Kaki  or  Oriental  Persimmon. 

Selections  of  Stocks  in  Citrus  Propagation. 

The  Effects  of  Alkali  on  Citrus  Trees. 

Control  of  the  Coyote  in  California. 

Commercial  Production  of  Grape  Syrup. 

Heavy  vs.  Light  Grain  Feeding  for  Dairy 
Cows. 

Storage  of  Perishable  Fruit  at  Freezing 
Temperatures. 
325.  Rice   Irrigation    Measurements   and   Ex- 
periments in  Sacramento  Valley,  1914- 
1919. 

Prune  Growing  in  California. 

Dehydration  of  Fruits. 

Phylloxera-Resistant  Stocks. 

Walnut  Culture  in  California. 

Preliminary  Volume  Tables  for  Second- 
Growth  Redwoods. 

Cocoanut  Meal  as  a  Feed  for  Dairy  Cows 
and  Other  Livestock. 

The  Preparation  of  Nicotine  Dust  as  an 
Insecticide. 
337.  Some  Factors  of  Dehydrater  Efficiency. 


308. 


309. 

310. 
312. 
313. 
316. 
317. 
318. 
320. 
321. 
323. 

324. 


328. 
330. 
331. 
332. 
334. 

335. 

336. 


CIRCULARS 


No. 

70.  Observations  on  the  Status  of  Corn 
Growing  in  California. 

82.  The  Common  Ground  Squirrels  of  Cali- 
fornia. 

87.  Alfalfa. 

110.  Green  Manuring  in  California. 

111.  The  Use  of  Lime  and  Gypsum  on  Cali- 

fornia Soils. 
113.  Correspondence  Courses  in  Agriculture. 
115.  Grafting  Vinifera  Vineyards. 

126.  Spraying  for  the  Grape  Leaf  Hopper. 

127.  House  Fumigation. 

128.  Insecticide  Formulas. 

129.  The  Control  of  Citrus  Insects. 

130.  Cabbage  Growing  in  California. 
135.  Official  Tests  of  Dairy  Cows. 
138.  The  Silo  in  California  Agriculture. 

144.  Oidium  or  Powdery  Mildew  of  the  Vine. 
148.  "Lungworms." 

151.  Feeding  and  Management  of  Hogs. 

152.  Some  Observations  on  the  Bulk  Handling 

of  Grain  in  California. 

153.  Announcement    of    the    California    State 

Dairy  Cow  Competition,  1916-18. 

154.  Irrigation    Practice    in    Growing    Small 

Fruits  in  California. 

155.  Bovine  Tuberculosis. 

157.  Control  of  the  Pear  Scab. 

158.  Home  and  Farm  Canning. 

159.  Agriculture  in  the  Imperial  Valley. 

160.  Lettuce  Growing  in  California. 

161.  Potatoes  in  California. 

164.  Small  Fruit  Culture  in  California. 


No. 

165.  Fundamentals    of    Sugar    Beet    Culture 

under  California  Conditions. 

166.  The  County  Farm  Bureau. 

167.  Feeding  Stuffs  of  Minor  Importance. 

169.  The  1918  Grain  Crop. 

170.  Fertilizing  California  Soils  for  the   1918 

Crop. 

172.  Wheat  Culture. 

173.  The  Construction  of  the  Wood-Hoop  Silo. 
Farm  Drainage  Methods. 
Progress   Report  on  the   Marketing  and 

Distribution  of  Milk. 
Hog  Cholera  Prevention  and  the  Serum 

Treatment. 
Grain  Sorghums. 

The  Packing  of  Apples  in  California. 
Factors  of  Importance  in  Producing  Milk 

of  Low  Bacterial  Count. 

181.  Control  of  the  California  Ground  Squirrel. 

182.  Extending  the  Area  of  Irrigated  Wheat  in 

California  for  1918. 

183.  Infectious  Abortion  in  Cows. 

184.  A  Flock  of  Sheep  on  the  Farm. 

188.  Lambing  Sheds. 

189.  Winter  Forage  Crops. 

190.  Agriculture  Clubs  in  California. 
193.  A  Study  of  Farm  Labor  in  California. 

Syrup  from  Sweet  Sorghum. 

Helpful  Hints  to  Hog  Raisers. 

County  Organizations  for  Rural  Fire  Con- 
trol. 

203.  Peat  as  a  Manure  Substitute. 
205.  Blackleg. 


174. 
175. 

176. 

177. 

178. 
179. 


198 
201 
202 


CIRCULARS — Continued 


No. 

206.  Jack  Cheese. 

208.  Summary  of  the  Annual  Reports  of  the 

Farm  Advisors  of  California. 

209.  The  Function  of  the  Farm  Bureau. 

210.  Suggestions  to  the  Settler  in  California. 
212.  Salvaging  Rain-Damaged  Prunes. 

214.  Seed   Treatment   for   the   Prevention    of 

Cereal  Smuts. 

215.  Feeding  Dairy  Cows  in  California. 

217.  Methods    for    Marketing    Vegetables    in 

California. 

218.  Advanced  Registry  Testing  of  Dairy  Cows. 

219.  The  Present  Status  of  Alkali. 

220.  Unfermented  Fruit  Juices. 

221.  How  California  is  Helping  People   Own 

Farms  and  Rural  Homes. 

223.  The  Pear  Thrips. 

224.  Control  of  the  Brown  Apricot  Scale  and 

the    Italian   Pear   Scale   on    Deciduous 
Fruit  Trees. 


No. 

225.  Propagation  of  Vines. 

227.  Plant  Diseases  and  Pest  Control. 

228.  Vineyard  Irrigation  in  Arid  Climates. 

229.  Cordon  Pruning. 

230.  Testing  Milk,  Cream,  and  Skim  Milk  for 

Butterfat. 

231.  The  Home  Vineyard. 

232.  Harvesting      and      Handling      California 

Cherries  for  Eastern  Shipment. 

233.  Artificial  Incubation. 

234.  Winter   Injury  to  Young  Walnut  Trees 

During  1921-22. 

235.  Soil  Analyses  and  Soil  and  Plant  Inter- 

relations. 


